PostgreSQL 源码解读（205）- 查询#118(数据结构RangeTblEntry)

/*-------------------- * RangeTblEntry - * A range table is a List of RangeTblEntry nodes. * RangeTblEntry节点链表 * * A range table entry may represent a plain relation, a sub-select in * FROM, or the result of a JOIN clause. (Only explicit JOIN syntax * produces an RTE, not the implicit join resulting from multiple FROM * items. This is because we only need the RTE to deal with SQL features * like outer joins and join-output-column aliasing.) Other special * RTE types also exist, as indicated by RTEKind. * RTE可能是普通表/FROM中的子查询/JOIN语句的结果. * (只有显示的JOIN语法会产生RTE,由多个FROM项生成的隐式连接则不会生成.这是因为 * 我们只需要RTE来处理SQL特性,比如外部连接和连接输出列别名) * * Note that we consider RTE_RELATION to cover anything that has a pg_class * entry. relkind distinguishes the sub-cases. * 注意RTE_RELATION指代了存储在pg_class中的relation信息. * * alias is an Alias node representing the AS alias-clause attached to the * FROM expression, or NULL if no clause. * alias是FROM表达式中AS别名子句中的Alias节点. * * eref is the table reference name and column reference names (either * real or aliases). Note that system columns (OID etc) are not included * in the column list. * eref->aliasname is required to be present, and should generally be used * to identify the RTE for error messages etc. * eref是表和列引用名称.要注意的是系统列(如OID)不在列链表中. * * In RELATION RTEs, the colnames in both alias and eref are indexed by * physical attribute number; this means there must be colname entries for * dropped columns. When building an RTE we insert empty strings ("") for * dropped columns. Note however that a stored rule may have nonempty * colnames for columns dropped since the rule was created (and for that * matter the colnames might be out of date due to column renamings). * The same comments apply to FUNCTION RTEs when a function's return type * is a named composite type. * 在RELATION RTEs中,别名和eref都通过物理属性编号来索引. * * In JOIN RTEs, the colnames in both alias and eref are one-to-one with * joinaliasvars entries. A JOIN RTE will omit columns of its inputs when * those columns are known to be dropped at parse time. Again, however, * a stored rule might contain entries for columns dropped since the rule * was created. (This is only possible for columns not actually referenced * in the rule.) When loading a stored rule, we replace the joinaliasvars * items for any such columns with null pointers. (We can't simply delete * them from the joinaliasvars list, because that would affect the attnums * of Vars referencing the rest of the list.) * 在JOIN RTEs中,不管是别名还是eref与joinaliasvars是一一对应的. * JOIN RTE会省略掉在解析阶段发现的需要drop的列. * 但是,已存储的规则可能包含已drop的列. * * inh is true for relation references that should be expanded to include * inheritance children, if the rel has any. This *must* be false for * RTEs other than RTE_RELATION entries. * 如关系引用需要扩展用于包含继承子关系,则inh字段为T.除了RTE_RELATION条目,其他RTEs必须为F. * * inFromCl marks those range variables that are listed in the FROM clause. * It's false for RTEs that are added to a query behind the scenes, such * as the NEW and OLD variables for a rule, or the subqueries of a UNION. * This flag is not used anymore during parsing, since the parser now uses * a separate "namespace" data structure to control visibility, but it is * needed by ruleutils.c to determine whether RTEs should be shown in * decompiled queries. * inFromCl标记了FROM语句包含了哪些RangeVar. * 在解析阶段,该标记不会使用,因为解析器使用独立的"namespace"数据结构来控制可见性, * 但在ruleutils.c中需要用到该标记来确定RTEs是否在反编译查询中显示. * * requiredPerms and checkAsUser specify run-time access permissions * checks to be performed at query startup. The user must have *all* * of the permissions that are OR'd together in requiredPerms (zero * indicates no permissions checking). If checkAsUser is not zero, * then do the permissions checks using the access rights of that user, * not the current effective user ID. (This allows rules to act as * setuid gateways.) Permissions checks only apply to RELATION RTEs. * requiredPerms和checkAsUser用于表示在查询启动时需要检查的运行时访问权限. * * For SELECT/INSERT/UPDATE permissions, if the user doesn't have * table-wide permissions then it is sufficient to have the permissions * on all columns identified in selectedCols (for SELECT) and/or * insertedCols and/or updatedCols (INSERT with ON CONFLICT DO UPDATE may * have all 3). selectedCols, insertedCols and updatedCols are bitmapsets, * which cannot have negative integer members, so we subtract * FirstLowInvalidHeapAttributeNumber from column numbers before storing * them in these fields. A whole-row Var reference is represented by * setting the bit for InvalidAttrNumber. * 对于SELECT/INSERT/UPDATE权限,如果用户没有表级权限,但有足够的权限访问在 * selectedCols (SELECT) and/or * insertedCols and/or updatedCols (INSERT with ON CONFLICT DO UPDATE may * have all 3)中定义的列. * * updatedCols is also used in some other places, for example, to determine * which triggers to fire and in FDWs to know which changed columns they * need to ship off. Generated columns that are caused to be updated by an * update to a base column are collected in extraUpdatedCols. This is not * considered for permission checking, but it is useful in those places * that want to know the full set of columns being updated as opposed to * only the ones the user explicitly mentioned in the query. (There is * currently no need for an extraInsertedCols, but it could exist.) * updatedCols可能会用于其他地方,比如用于确定哪个触发器会被触发,在FDWs中哪些修改的列需要发送等. * * securityQuals is a list of security barrier quals (boolean expressions), * to be tested in the listed order before returning a row from the * relation. It is always NIL in parser output. Entries are added by the * rewriter to implement security-barrier views and/or row-level security. * Note that the planner turns each boolean expression into an implicitly * AND'ed sublist, as is its usual habit with qualification expressions. * securityQuals是安全栏表达式链表(布尔表达式),在返回行前用于校验. *-------------------- */ typedef enum RTEKind { //常规的关系引用 RTE_RELATION, /* ordinary relation reference */ //FROM中的子查询 RTE_SUBQUERY, /* subquery in FROM */ //JOIN RTE_JOIN, /* join */ //FROM中的函数 RTE_FUNCTION, /* function in FROM */ //TableFunc(..,列链表) RTE_TABLEFUNC, /* TableFunc(.., column list) */ //VALUES (<exprlist>), (<exprlist>), ... RTE_VALUES, /* VALUES (<exprlist>), (<exprlist>), ... */ //CTE RTE_CTE, /* common table expr (WITH list element) */ //tuplestore,比如AFTER触发器 RTE_NAMEDTUPLESTORE, /* tuplestore, e.g. for AFTER triggers */ //表示空的FROM语句.通过规划器添加,在解析和重写阶段不会出现 RTE_RESULT /* RTE represents an empty FROM clause; such * RTEs are added by the planner, they're not * present during parsing or rewriting */ } RTEKind; typedef struct RangeTblEntry { NodeTag type; //详见上述说明 RTEKind rtekind; /* see above */ /* * XXX the fields applicable to only some rte kinds should be merged into * a union. I didn't do this yet because the diffs would impact a lot of * code that is being actively worked on. FIXME someday. */ /* * Fields valid for a plain relation RTE (else zero): * 以下字段对普通关系RTE有用(其他类型的RTE,值为0) * * As a special case, RTE_NAMEDTUPLESTORE can also set relid to indicate * that the tuple format of the tuplestore is the same as the referenced * relation. This allows plans referencing AFTER trigger transition * tables to be invalidated if the underlying table is altered. * 作为一个特例,RTE_NAMEDTUPLESTORE可设置relid,用以表示该tuple是属于哪个relation的. * * rellockmode is really LOCKMODE, but it's declared int to avoid having * to include lock-related headers here. It must be RowExclusiveLock if * the RTE is an INSERT/UPDATE/DELETE target, else RowShareLock if the RTE * is a SELECT FOR UPDATE/FOR SHARE target, else AccessShareLock. * rellockmode是实际的LOCKMODE,定义为int类型是为了避免包含锁相关的头文件. * 如果RTE是INSERT/UPDATE/DELETE,必须是RowExclusiveLock, * 如果是SELECT FOR UPDATE/FOR SHARE,是RowShareLock * 否则,是AccessShareLock * * Note: in some cases, rule expansion may result in RTEs that are marked * with RowExclusiveLock even though they are not the target of the * current query; this happens if a DO ALSO rule simply scans the original * target table. We leave such RTEs with their original lockmode so as to * avoid getting an additional, lesser lock. */ Oid relid; /* OID of the relation */ char relkind; /* relation kind (see pg_class.relkind) */ int rellockmode; /* lock level that query requires on the rel */ struct TableSampleClause *tablesample; /* sampling info, or NULL */ /* * Fields valid for a subquery RTE (else NULL): * 用于子查询 */ //子查询 Query *subquery; /* the sub-query */ //来自于安全栏视图? bool security_barrier; /* is from security_barrier view? */ /* * Fields valid for a join RTE (else NULL/zero): * 用于连接RTE(否则为NULL/0) * * joinaliasvars is a list of (usually) Vars corresponding to the columns * of the join result. An alias Var referencing column K of the join * result can be replaced by the K'th element of joinaliasvars --- but to * simplify the task of reverse-listing aliases correctly, we do not do * that until planning time. In detail: an element of joinaliasvars can * be a Var of one of the join's input relations, or such a Var with an * implicit coercion to the join's output column type, or a COALESCE * expression containing the two input column Vars (possibly coerced). * Within a Query loaded from a stored rule, it is also possible for * joinaliasvars items to be null pointers, which are placeholders for * (necessarily unreferenced) columns dropped since the rule was made. * Also, once planning begins, joinaliasvars items can be almost anything, * as a result of subquery-flattening substitutions. * joinaliasvars是对应join结果的Vars链表. * 引用连接结果列K的别名Var可以通过joinaliasvars中的第K个元素代替,这一步在计划阶段才去做. */ JoinType jointype; /* type of join */ List *joinaliasvars; /* list of alias-var expansions */ /* * Fields valid for a function RTE (else NIL/zero): * 函数RTE * * When funcordinality is true, the eref->colnames list includes an alias * for the ordinality column. The ordinality column is otherwise * implicit, and must be accounted for "by hand" in places such as * expandRTE(). * funcordinality为T,则eref->colnames链表包含原列的别名. */ List *functions; /* list of RangeTblFunction nodes */ bool funcordinality; /* is this called WITH ORDINALITY? */ /* * Fields valid for a TableFunc RTE (else NULL): * 用于TableFunc RTE */ TableFunc *tablefunc; /* * Fields valid for a values RTE (else NIL): * 用于Values RTE */ List *values_lists; /* list of expression lists */ /* * Fields valid for a CTE RTE (else NULL/zero): * 用于CTE RTE */ //WITH链表条目名称 char *ctename; /* name of the WITH list item */ //查询层次编号 Index ctelevelsup; /* number of query levels up */ //是否递归? bool self_reference; /* is this a recursive self-reference? */ /* * Fields valid for CTE, VALUES, ENR, and TableFunc RTEs (else NIL): * 用于CTE, VALUES, ENR, and TableFunc RTEs * * We need these for CTE RTEs so that the types of self-referential * columns are well-defined. For VALUES RTEs, storing these explicitly * saves having to re-determine the info by scanning the values_lists. For * ENRs, we store the types explicitly here (we could get the information * from the catalogs if 'relid' was supplied, but we'd still need these * for TupleDesc-based ENRs, so we might as well always store the type * info here). For TableFuncs, these fields are redundant with data in * the TableFunc node, but keeping them here allows some code sharing with * the other cases. * CTE : 自引用列可被定义. * VALUES : 显式存储这些信息可以避免扫描values_lists. * ENRs : 显式存储 * TableFuncs : 这些字段与TableFunc节点中的数据重复,用于共享信息 * * For ENRs only, we have to consider the possibility of dropped columns. * A dropped column is included in these lists, but it will have zeroes in * all three lists (as well as an empty-string entry in eref). Testing * for zero coltype is the standard way to detect a dropped column. * 对于ERNs,不得不考虑已删除字段的可能性. */ List *coltypes; /* OID list of column type OIDs */ List *coltypmods; /* integer list of column typmods */ List *colcollations; /* OID list of column collation OIDs */ /* * Fields valid for ENR RTEs (else NULL/zero): * ENR RTEs的字段 */ char *enrname; /* name of ephemeral named relation */ double enrtuples; /* estimated or actual from caller */ /* * Fields valid in all RTEs: * 所有RTE都有的字段 */ //用户自定义别名 Alias *alias; /* user-written alias clause, if any */ //已扩展的引用名 Alias *eref; /* expanded reference names */ //子查询/函数/VALUES是LATERAL bool lateral; /* subquery, function, or values is LATERAL? */ //是否继承? bool inh; /* inheritance requested? */ //在FROM中出现? bool inFromCl; /* present in FROM clause? */ //访问权限位掩码 AclMode requiredPerms; /* bitmask of required access permissions */ //如有效,则使用此角色检查访问权限 Oid checkAsUser; /* if valid, check access as this role */ //需要SELECT的权限 Bitmapset *selectedCols; /* columns needing SELECT permission */ Bitmapset *insertedCols; /* columns needing INSERT permission */ Bitmapset *updatedCols; /* columns needing UPDATE permission */ //将要被update的列 Bitmapset *extraUpdatedCols; /* generated columns being updated */ //需应用的安全栏 List *securityQuals; /* security barrier quals to apply, if any */ } RangeTblEntry;

-- 用于测试的查询语句 testdb=# select * from ( testdb(# select t_dwxx.dwmc,t_grxx.grbh,t_grxx.xm,t_jfxx.ny,t_jfxx.je testdb(# from t_dwxx inner join t_grxx on t_dwxx.dwbh = t_grxx.dwbh testdb(# inner join t_jfxx on t_grxx.grbh = t_jfxx.grbh testdb(# where t_dwxx.dwbh IN ('1001') testdb(# union all testdb(# select t_dwxx.dwmc,t_grxx.grbh,t_grxx.xm,t_jfxx.ny,t_jfxx.je testdb(# from t_dwxx inner join t_grxx on t_dwxx.dwbh = t_grxx.dwbh testdb(# inner join t_jfxx on t_grxx.grbh = t_jfxx.grbh testdb(# where t_dwxx.dwbh IN ('1002') testdb(# ) as ret testdb-# order by ret.grbh testdb-# limit 4;

... (gdb) set $rtable=$query->rtable (gdb) p *$rtable $8 = {type = T_List, length = 3, head = 0x170be48, tail = 0x170f6b0} (gdb) p *(Node *)($rtable->head->data.ptr_value) $9 = {type = T_RangeTblEntry} (gdb) p *(RangeTblEntry *)($rtable->head->data.ptr_value) $10 = {type = T_RangeTblEntry, rtekind = RTE_SUBQUERY, relid = 0, relkind = 0 '\000', tablesample = 0x0, subquery = 0x1667500, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0, funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0, self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0, enrtuples = 0, alias = 0x1666d40, eref = 0x170bc18, lateral = false, inh = true, inFromCl = true, requiredPerms = 2, checkAsUser = 0, selectedCols = 0x0, insertedCols = 0x0, updatedCols = 0x0, securityQuals = 0x0} (gdb) set $rte=(RangeTblEntry *)($rtable->head->data.ptr_value) (gdb) p *$rte->subquery $12 = {type = T_Query, commandType = CMD_SELECT, querySource = QSRC_ORIGINAL, queryId = 0, canSetTag = true, utilityStmt = 0x0, resultRelation = 0, hasAggs = false, hasWindowFuncs = false, hasTargetSRFs = false, hasSubLinks = false, hasDistinctOn = false, hasRecursive = false, hasModifyingCTE = false, hasForUpdate = false, hasRowSecurity = false, cteList = 0x0, rtable = 0x16fe4e8, jointree = 0x170bbe8, targetList = 0x170b358, override = OVERRIDING_NOT_SET, onConflict = 0x0, returningList = 0x0, groupClause = 0x0, groupingSets = 0x0, havingQual = 0x0, windowClause = 0x0, distinctClause = 0x0, sortClause = 0x0, limitOffset = 0x0, limitCount = 0x0, rowMarks = 0x0, setOperations = 0x1667610, constraintDeps = 0x0, withCheckOptions = 0x0, stmt_location = 0, stmt_len = 0} (gdb) p *$rte->alias $13 = {type = T_Alias, aliasname = 0x1666d28 "ret", colnames = 0x0} (gdb) p *$rte->eref $14 = {type = T_Alias, aliasname = 0x170bc48 "ret", colnames = 0x170bcb8} (gdb) p *$rte->eref->colnames $15 = {type = T_List, length = 5, head = 0x170bc98, tail = 0x170be28} (gdb) p *(Node *)$rte->eref->colnames->head->data.ptr_value $16 = {type = T_String} (gdb) p *(Value *)$rte->eref->colnames->head->data.ptr_value $17 = {type = T_String, val = {ival = 24165472, str = 0x170bc60 "dwmc"}} ---->subquery (gdb) p *(RangeTblEntry *)$rte->subquery->rtable->head->data.ptr_value $26 = {type = T_RangeTblEntry, rtekind = RTE_SUBQUERY, relid = 0, relkind = 0 '\000', tablesample = 0x0, subquery = 0x16faf98, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0, funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0, self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0, enrtuples = 0, alias = 0x16fe240, eref = 0x16fe290, lateral = false, inh = false, inFromCl = false, requiredPerms = 0, checkAsUser = 0, selectedCols = 0x0, insertedCols = 0x0, updatedCols = 0x0, securityQuals = 0x0} (gdb) set $rte_sq_rte=((RangeTblEntry *)$rte->subquery->rtable->head->data.ptr_value) (gdb) p *(RangeTblEntry *)$rte_sq_rte->subquery->rtable->head->data.ptr_value $30 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26754, relkind = 114 'r', tablesample = 0x0, subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0, funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0, self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0, enrtuples = 0, alias = 0x0, eref = 0x16677c0, lateral = false, inh = true, inFromCl = true, requiredPerms = 2, checkAsUser = 0, selectedCols = 0x16fbda8, insertedCols = 0x0, updatedCols = 0x0, securityQuals = 0x0} (gdb) set $rte_sq_rte_sq_rte=(RangeTblEntry *)$rte_sq_rte->subquery->rtable->head->data.ptr_value (gdb) p *$rte_sq_rte_sq_rte $42 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26754, relkind = 114 'r', tablesample = 0x0, subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0, funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0, self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0, enrtuples = 0, alias = 0x0, eref = 0x16677c0, lateral = false, inh = true, inFromCl = true, requiredPerms = 2, checkAsUser = 0, selectedCols = 0x16fbda8, insertedCols = 0x0, updatedCols = 0x0, securityQuals = 0x0} (gdb) set $rte_sq_rte_sq_rtable=$rte_sq_rte->subquery->rtable (gdb) p *(RangeTblEntry *)($rte_sq_rte_sq_rtable->head->data.ptr_value) $60 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26754, relkind = 114 'r', tablesample = 0x0, subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0, funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0, self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0, enrtuples = 0, alias = 0x0, eref = 0x16677c0, lateral = false, inh = true, inFromCl = true, requiredPerms = 2, checkAsUser = 0, selectedCols = 0x16fbda8, insertedCols = 0x0, updatedCols = 0x0, securityQuals = 0x0} (gdb) p *(RangeTblEntry *)($rte_sq_rte_sq_rtable->head->next->data.ptr_value) $61 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26757, relkind = 114 'r', tablesample = 0x0, subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0, funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0, self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0, enrtuples = 0, alias = 0x0, eref = 0x16fb4f0, lateral = false, inh = true, inFromCl = true, requiredPerms = 2, checkAsUser = 0, selectedCols = 0x16fbe10, insertedCols = 0x0, updatedCols = 0x0, securityQuals = 0x0} (gdb) p *(RangeTblEntry *)($rte_sq_rte_sq_rtable->head->next->next->data.ptr_value) $62 = {type = T_RangeTblEntry, rtekind = RTE_JOIN, relid = 0, relkind = 0 '\000', tablesample = 0x0, subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x16fbff8, functions = 0x0, funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0, self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0, enrtuples = 0, alias = 0x0, eref = 0x16fc318, lateral = false, inh = false, inFromCl = true, requiredPerms = 0, checkAsUser = 0, selectedCols = 0x0, insertedCols = 0x0, updatedCols = 0x0, securityQuals = 0x0} (gdb) p *(RangeTblEntry *)($rte_sq_rte_sq_rtable->head->next->next->next->data.ptr_value) $63 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26760, relkind = 114 'r', tablesample = 0x0, subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0, funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0, self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0, enrtuples = 0, alias = 0x0, eref = 0x16fc678, lateral = false, inh = true, inFromCl = true, requiredPerms = 2, checkAsUser = 0, selectedCols = 0x16fd1d0, insertedCols = 0x0, updatedCols = 0x0, securityQuals = 0x0} (gdb) p *(RangeTblEntry *)($rte_sq_rte_sq_rtable->tail->data.ptr_value) $64 = {type = T_RangeTblEntry, rtekind = RTE_JOIN, relid = 0, relkind = 0 '\000', tablesample = 0x0, subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x16fd3b8, functions = 0x0, funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0, self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0, enrtuples = 0, alias = 0x0, eref = 0x16fd798, lateral = false, inh = false, inFromCl = true, requiredPerms = 0, checkAsUser = 0, selectedCols = 0x0, insertedCols = 0x0, updatedCols = 0x0, securityQuals = 0x0}

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一、数据结构

二、源码解读

三、跟踪分析

四、参考资料

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